A hydro pneumatic accumulator is conceptually a device wherein one fluid under pressure is utilized as potential energy for performing useful work through the medium of another fluid. A hydro pneumatic accumulator is typically used in a hydraulic system for preventing the pressure of a hydraulic fluid, e.g., an oil, from rising excessively or falling suddenly due to temporary accumulating or discharging of oil or any turbulence in the hydraulic system. For example, the accumulator temporarily accumulates oil fed from a pump while a fluid-actuated device such as a hydraulic motor is turned off. When the device is actuated again, the accumulator discharges accumulated oil and feeds it rapidly to the device until more oil from the pump reaches the device. Another example is hydraulic control of electric circuit breakers.
The accumulator is generally classified as either a flexible gas chamber type accumulator or a piston type accumulator. A flexible gas chamber type accumulator usually comprises a cylindrical shell and a gas recharged bladder or diaphragm or bellow incorporated therein, which is inflated and deflated in response to the change of pressure of liquid contained in the hydraulic system. A piston type accumulator comprises a cylindrical shell and a reciprocating piston therein, conceptually floating, which changes the volume of liquid chamber and that of a gas chamber bounded thereby. U.S. Pat. No. 3,613,734A discloses such a piston type accumulator. A combination type accumulator is also known as disclosed in U.S. Pat. No. 2,688,984.
While piston type accumulator has proven to be robust and naturally dampening the pressure spikes encountered in the use, inter-chamber leakage, primarily from periphery of the piston is a known challenge. Multiple piston rings and seals are provided, to check inter-chamber leakage. Patent application with International Publication Number WO1989/03483 discloses a seal ring in the end cover as a valve which prevents the gas from escaping from the accumulator if it is completely emptied for fluid.
All seals and preventive measures have a life, which varies and therefore, it remains unknown as to when the inter-chamber leakage commences. Some users top up the gas chamber periodically to combat such unpredictability.
There is a need in the art to detect inter-chamber leak early enough and take corrective action.